1. Field of the Invention
The invention relates to a process for the production of coated substrates and to the coated substrates.
2. Description of the Prior Art
WO 98/23390 discloses a coating process in which a primer, which is electrically conductive when baked, is coil coated onto both sides of a metal sheet and is baked and sheet metal parts are then stamped out of the sheets coated in this way and are shaped by deep-drawing. These coated sheet metal parts may then be assembled to form a construction, for example, a motor vehicle body. After shaping and optionally assembly, a base coat/clear coat two-layer coating is applied, either the base coat or, if an intermediate coat is applied before application of the base coat, the intermediate coat is applied by electrodeposition, (ED coating). An essential feature is that the primer applied by the coil coating process is applied sufficiently thinly to have sufficient electrical conductivity for subsequent ED coating and/or the coil coating composition contains components which impart electrical conductivity.
In the past, a coating process, which became known as the “reverse process”, was used, wherein initially a primer surfacer layer was spray-applied directly to the metal outer skin of a car body and baked. Then, an ED coating primer was applied to the metal surfaces inside the car body, which had remained uncoated, and baked (see G. Fettis, Automotive paints and coatings, Verlag Chemie, Weinheim, 1995, pages 61-63).